Nucleotide sequence analysis of the DNA binding region of the chicken fibronectin gene

We have determined the nucleotide sequence of 2.0 kb EcoRI segment from the clone lambda FC32 of the genomic chicken fibronectin gene, which is called DNA binding domain. This segment overlapped another clone lambda FC36 and contained three exons which were 16, 17 and 18. They were classified as Type III repeat as originally shown in bovine plasma fibronectin. The average homologies of these three exons among the chicken, rat and human fibronectins in amino acid level are very high (87-98%) compared with that (79-88%) of the exons in the cell binding domain, indicating that this region is highly conservative during the evolution.